Head mounted display system with aspheric optics

ABSTRACT

A binocular head mounted display system is shown utilizing an aspheric lens in each of the user&#39;s right-eye and left-eye optical paths. The aspheric lens is formed with a number of concentric zones for controlling the distance at which an image of displayed information is projected from the user and to minimize distortions across the virtual image. The distance between each lens and its respective display is independently variable. Further, the distance between the optical system as a whole and the user&#39;s eyes is variable.

This is a continuation-in-part of U.S. patent application Ser. No.08/133,521 filed Oct. 7, 1993.

TECHNICAL FIELD

The present invention is directed to a head mounted display system andmore particularly to a head mounted display system that employs acompact, optical system with an aspheric lens for minimizing distortionsacross the virtual image projected by the system.

BACKGROUND OF THE INVENTION

Head mounted display systems are known that include a lens disposedbetween an eye of the user and the face of a display for projecting anenlarged virtual image of the displayed information. These systems,however, typically employ a lens with a simple curvature such as aspherical lens. The virtual image that results with the use of aspherical lens has a number of distortions, including variations in themagnification and field of curvature across the image as well as edgedistortions such as barrel distortion. In order to compensate for suchdistortions compensating lenses and the like are typically added to theoptical system. These additional optics, however, increase the weightand overall size of the optical system. It is important to minimize theweight and size of the optical system for a head mounted display unit,otherwise the unit is too heavy and cumbersome to be comfortablysupported on a user's head.

SUMMARY OF THE INVENTION

In accordance with the present invention, the disadvantages of priorhead mounted display systems have been overcome. The head mounteddisplay system of the present invention utilizes an aspheric lens thatcontrols the distance from the user at which the virtual image appearsand that further substantially eliminates distortions across the virtualimage.

More particularly, the head mounted display system of the presentinvention includes a support to mount the display system on a user'shead. An image source is mounted on the support to provide videoinformation. The aspheric lens is mounted on the support relative to theimage source to allow a user to view, through the aspheric lens, anenlarged image of the video with the image being projected at a distancefrom the user. The aspheric lens has a surface shaped with a number ofconcentric zones that includes an inner-zone for substantiallycontrolling the distance from the user at which the virtual imageappears and one or more zones located outside of the inner-zone tominimize distortions across the virtual image. In one embodiment, amid-zone minimizes variations in magnification and field of curvatureacross the virtual image and an outer-zone minimizes distortions aboutthe edges of the virtual image.

The aspheric lens may include a single aspheric surface as describedabove. Alternatively, the aspheric lens may be biaspheric, including anaspheric entrance surface and an aspheric exit surface. Further, theaspheric lens may be formed of at least two materials having differentindices of refraction so as to form an achromat to compensate forchromatic aberrations.

The aspheric lens, in accordance with the present invention, may beutilized in a monocular head mounted display system. Alternatively, twoaspheric lenses, one associated with the user's right eye and oneassociated with the user's left eye, may be employed with a singledisplay or a pair of displays or image sources so as to provide abinocular head mounted display system.

The aspheric lens and display are mounted on the support such that thelens is substantially parallel to the face of the display, wherein acentral axis of the lens extends perpendicular to the face of thedisplay. For systems in which the virtual image is to appear at adistance from the user that is less than infinity, the aspheric lens anddisplay are mounted on the support at a convergence angle with respectto the axis of a user's eye when looking straight ahead. The lens anddisplay are at a convergence angle with respect to the user's eye todirect the user's eye inward at an angle that is natural for a userviewing an object at a distance that is less than infinity.

The aspheric lens and display are further mounted on the supportrelative to one another such that the distance between the lens anddisplay is variable. For a binocular head mounted display system, thedistance between the right-eye lens and display and the distance betweenthe left-eye lens and display are independently variable. Because thedistances between the lens and display are independently variable forthe user's right and left eye, the distance of each lens may be set by aparticular user so as to accommodate for refractive error in user's thatare near-sighted or far-sighted. Thus, the head mounted display systemof the present invention may be worn by a user who normally wearscorrective eyewear, without that eyewear.

Further, in order to compensate for variations in the interpupillarydistance of various users, the support on which the optics anddisplay(s) are mounted is movable with respect to the user's face toallow a user to vary the distance between the user's eyes and respectivelenses together.

These and other objects, advantages and novel features of the presentinvention, as well as details of an illustrative embodiment thereof,will be more fully understood from the following description and thedrawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective back view of the head mounted display system inaccordance with the present invention;

FIG. 2 is an exploded, perspective back view of the head mounted displaysystem depicted in FIG. 1;

FIG. 3 is an exploded front perspective front view of the head mounteddisplay system of FIG. 1;

FIG. 4 is a front perspective view of the head mounted display system ofFIG. 1;

FIG. 5 is a schematic illustration of the orientation of the displaysand optics of the system shown in FIG. 1 relative to a user's eye;

FIG. 6 is a schematic illustration of an aspheric lens with threeconcentric zones; and

FIGS. 7A and 7B are graphs illustrating how one aspheric surface of thelens varies with X;

FIG. 8 is a front perspective view of a head mounted display system inaccordance with the present invention utilizing a different support tomount the system on a user's head;

FIG. 9 is a partial front perspective view of the head mounted displaysystem shown in FIG. 8;

FIG. 10 is a back perspective view of a rotatable mounting and alaterally moveable mounting for the lens and display pairs of the systemof FIG. 8;

FIG. 11 is a back perspective view of the laterally moveable mountingfor the lens and display pairs of the system of FIG. 8; and

FIG. 12 is a schematic illustration of an alternative embodiment of theoptical system utilizing an aspheric lens in accordance with the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The head mounted display unit 10 of the present invention, as shown inFIGS. 1-4, includes a frame 12 having a support 14 for the opticalsystem. The support 14 includes a front cover 15 and is adjustablymounted on a pair of temples 16 and 18. The optical system of the headmounted display unit 10 includes a right-eye aspheric lens 20 and aleft-eye aspheric lens 22 into which a user looks to view an enlargedvirtual image of the video information depicted on respective displays24 and 26 where the virtual image appears at a distance from the userthat is greater than the actual distance of the display from the user.The displays 24 and 26 may be liquid crystal displays or the like whichare mounted on the support 14 such that the face 25, 27 of each display24, 26 is aligned with a respective aperture 29, 31 in the support 14with the face 25, 27 of each display 24, 26 being directed towards theuser.

The frame 12 also supports drive electronics for the displays 24 and 26,as well as for a pair of earphones 33 and 35. As is well known, thedrive electronics for the displays are responsive to standard videoinput signals to drive the displays to depict video information. Toreduce the weight of the head mounted display unit 10 and to allow thehead mounted display unit 10 to provide a universal video display thatmay receive video inputs from any one of a number of sources, the videoinput signal generator is preferably a separate, remote unit.

The video input signal generator may take the form of a televisiontuner, video camera, video player, video game, computer, or other devicethat generates a video input signal. In particular, the displays 24 and26 may be driven to provide a stereoscopic virtual image, as is wellknown. The head mounted display system 10 may be coupled to the videoinput signal generator and/or audio generator by a cable or the like;however, the unit 10 need not be physically connected to the video/audioinput signal generator. For example, the video and audio input signalsmay be RF modulated and transmitted from the remote unit to a headmounted display unit 10 that includes an RF receiver, as described indetailed in U.S. patent application Ser. No. 07/986,422, filed Dec. 4,1992, assigned to the Assignee of the present invention and incorporatedherein by reference.

Each of the aspheric lenses 20 and 22, as shown in FIG. 6 includes asurface shaped with a number of concentric zones I, II and III so as tomap a flat displayed video image onto the complex curvature of theuser's retina so that the virtual image appears without distortionstherein. The inner-zone I is substantially spherical and primarilycontrols the distance from the user at which the virtual image appears,i.e., the focal length of the lens 20, 22. A mid-zone II is flatter inradius than the inner-zone I and minimizes variations in magnificationand field of curvature across the virtual image. An outer-zone III isshaped so as to minimize distortions in the edges of the virtual imageso that the edges appear straight and each edge appears to be at rightangles with respect to its adjacent edge. In order to shape the asphericsurface of each lens 20, 22 so as to provide the inner, mid andouter-zones, each lens 20, 22 is designed in accordance with thefollowing equation: ##EQU1## where X represents sag and Y describes thesurface of the asphere as a function of X as shown in FIGS. 7A and 7B.In the above equation, R represents the central radius of curvature ofthe lens 20, 22 and C is equal to 1/R. R and C are the predominantfactors which characterize the inner-zone I. The constant, cc, whichrepresents the conic constant is the predominant factor controlling thesurface of the aspheric lens in the mid-zone II; whereas the constantsA2, A4 and A6 are the predominant factors in controlling the curvaturein the outer-zone III.

Each of the aspheric lenses 20, 22 may be formed as a biasphere havingan aspheric entrance surface adjacent the display and an aspheric exitsurface adjacent the user's eye. Each aspheric lens 20, 22 may be formedof a single, optically transmissive material with an index of refractionof approximately 1.49 although materials with other indices ofrefraction may be used as well. It is noted that as the index ofrefraction of the material increases, the radius of curvature of theaspheric surface(s) flattens. Alternatively, each aspheric lens 20, 22may be formed of at least two materials having different indices ofrefraction so as to form an achromat to compensate for chromaticaberrations. For a biaspheric lens with 2X magnification, the constantsfor the above-identified equation which describe the entrance surface ofthe lens are as follows:

R=27 mm-32 mm; cc=-1.0-+2.0;

A2=-0.01-+0.01; A4=+0.00005--0.00005;

and A6 may be set to zero. The constants of the above equation for theexit surface of such a biaspheric lens with 2X magnification are asfollows:

R=48 mm-55.5 mm; cc=+1.0--3.5;

A2=-0.01-+0.01; A4=+0.00005--0.00005; and A6 may be set to zero. Witheach aspheric lens 20 and 22 formed as such and with a display having awidth of 20 mm or 0.78 inches, the image through one of the lensesfocused at 10 feet from the user appears to be approximately 5 feet widewith an approximate field of view of 30°.

For a biaspheric lens of 1X magnification, the constants describing theentrance surface of the lens are as follows:

R=18.0 mm-13.6 mm; cc=+1.0--3.0;

A2=-0.01-+0.01; A4=+0.00005--0.00005; and A6 may be set to zero. Theconstants describing the exit surface of the lens for 1X magnificationare as follows:

R=22.0-30; cc=-1.5-+1.5;

A2=-0.01-+0.01; A4=+0.00005--0.00005; and A6 may be set to zero. Witheach aspheric lens 20 and 22 formed as such and with a display having awidth of 20 mm or 0.78 inches, the image through one of the lensesfocused at 10 feet from the user appears to be approximately 10 feetwide with an approximate field of view of 50°.

Further, for a biaspheric lens of 0.85X magnification, the constantsdescribing the entrance surface of the lens are as follows:

R=11.4 mm-13 mm; cc=-4.0-+1.0;

A2=-0.0002-+0.0002; A4=+0.00002--0.00002;

and A6=-0.0000005-+0.0000005. The constants for the exit surface of abiaspheric lens with 0.85X magnification are as follows:

R=15 mm-20 mm; cc=-4-0;

A2=-0.001-+0.001; A4=+0.00002--0.00002 and A6 =-0.0000001-+0.0000001.With each aspheric lens 20 and 22 formed as such and with a displayhaving a width of 20 mm or 0.78 inches, the image through one of thelenses focused at 10 feet from the user appears to be approximately 15feet wide with a field of view of 73°.

It is noted that for each of the above examples, an equivalent lens 20,22 may be formed by decreasing the power of one surface and increasingthe power of the opposite surface. Further, although not necessary, itis preferred that the entrance surface of the lens 20, 22 is formed withmore power than the exit surface.

The use of a single aspheric lens 20, 22 in each optical path of thesystem allows the head mounted display unit 10 to be very lightweightand compact. For example, the distance from the cover 15 to a back 60 ofthe support 14 representing the thickness of the optical system ismerely 2 inches. Even though the optical system is small and compact,the virtual image seen by a user is substantially without distortionstherein across the entire width of the image.

Each of the lenses 20, 22 is mounted in a respective lens holder 28, 30that is movably mounted on the support 14 in a respective, generallycylindrical aperture 32, 34. Protrusions 38 and 39 are positionedopposite to each other on the inner surface of the wall defining theaperture 32. The protrusions 38 and 39 engage a helical groove 36 formedabout the outer cylindrical surface of the lens holder 36 so that as thelens holder 36 is rotated in the aperture 32, the pins 38 and 39engaging the groove 28 move the lens 20 closer to the display 24 orfarther therefrom while maintaining the central axis of the lens 20perpendicular to the face 25 of the display 24 such that the displayface 25 is generally parallel to the aspheric lens 20. An aperture 43 isformed in the wall of the support 14 adjacent the lens holder 28 so thata user can manually engage the lens holder 28 to rotate the lens 20.

Similarly, protrusions 40 and 41 are positioned opposite to each otheron the inner surface of the wall defining the aperture 34. Theprotrusions 40 and 41 engage a helical groove 37 formed about the outercylindrical surface of the lens holder 30 so that as the lens holder 30is rotated in the aperture 34, the pins 40 and 41 engaging the groove 37move the lens 22 closer to the display 26 or farther therefrom whilemaintaining the central axis of the lens 22 perpendicular to the face 27of the display 26 such that the display face 27 is generally parallel tothe aspheric lens 22. An aperture 45 is formed in the wall of thesupport 14 adjacent the lens holder 30 so that a user can manuallyengage the lens holder 30 to rotate the lens 22.

For a head mounted display system in which the virtual image is to beprojected at a distance that is less than infinity from the user, thecylindrical apertures 32 and 34 of the support 14 are formed thereinsuch that the axes of the apertures 32, 34 are converging towards thedisplays. Therefore, if the central axis of each of the lenses 20, 22extends from the center of the lens 20, 22 to the center of therespective display 24, 26, the centers of the displays 24 and 26 will becloser than the centers of the aspheric lenses 20 and 22 as shown inFIG. 5. This convergence angle 8 is small, so as to direct a user's eyeinward from the axis of the eye when looking straight ahead. The user'seyes are directed inward at a natural angle to the location of thevirtual image at a distance that is less than infinity from the user.For example, for a virtual image that is to appear two-ten feet from theuser, a convergence angle of approximately 2°-4° is desired.

The head mounted display system 10 of the present invention accommodatesusers having various interpupillary distances by allowing the support 14for the optical system to be moved as an integral unit closer to theuser's eyes in a direction 50 or farther away therefrom in a direction52 as depicted in FIG. 4. In order to accomplish this adjustablemovement of the support 14, each of the temples 16 and 18 is formed witha respective slot 54 through which a screw 56 extends so that the screw56 can be screwed into a threaded aperture in the outer surface of aflange 58 of the support 14. By sliding the temple 18 in the directionof the arrows 50 or 52 and tightening the screw 56, the support 14 maybe moved towards or away from the user's face to vary the distancebetween the optical system and the user's eyes to thereby correct forthe user's individual interpupillary distance.

It is noted that because each of the aspheric lenses 20, 22 is alsoindependently movable with respect to the displays 24 and 26, the lensesmay be individually moved towards or away from the displays so as toaccommodate for refractive error in each of the user's eyes for usersthat are near-sighted or far-sighted. Thus, the head mounted displaysystem of the present invention may be worn by a user who normally wearscorrective eyewear, without that eyewear.

FIGS. 8-11 illustrate another embodiment of the frame for a slightlymodified support 14' of the optical system that allows the support 14'to be rotated as well as to be moved along a linear path towards andaway from the user's eyes. More particularly, the support 14' is formedwithout the flanges 58 depicted in FIGS. 1-4. Instead, the support 14'is slidably mounted in a housing 70 that is in turn rotatably mounted ona frame 72. When the frame 72 is worn on a user's head, the frame 72 maybe positioned such that the lenses 20 and 22 as well as the respectivedisplays 24 and 26 are positioned directly in front of the user's eyes.Alternatively, the frame 72 may be worn higher on the user's head sothat the user looks slightly up to view the virtual image. In order toallow the user to look up into the lenses 20, 22, generally along thecentral axes thereof, the housing 70 is rotatable in the frame 72 sothat the user can align his eyes with the central axis of the respectivelenses 20, 22. It is noted that even if the frame 72 is worn such thatthe lenses 20, 22 are positioned directly in front of the user's eyes,the housing 70 may be rotated on the frame 72 slightly so as toaccommodate various users and to allow them to easily align the centralaxis of each lens 20, 22 with their eyes.

In order to allow the housing 70 and thus the support 14' with lenses20, 22 and displays 24, 26 to rotate, the housing 70 is formed with acylindrical protrusion 74 and 76 extending from opposite sides 78 and 80of the housing 70. The protrusions 74 and 76 extend into respectiveapertures 82 formed in the frame 72 so that the protrusions can rotatetherein. The lower portion of each aperture 82 is formed in a respectivebottom cover 86 and 88 of the frame 72 whereas the upper portion of eachaperture is formed in a top cover 90 of the frame 72.

The support 14' is slidably mounted in the housing 70 so that theoptical system can be moved as an integral unit closer to or fartheraway from the user's eyes in order to accommodate users having variousinterpupillary distances as discussed above. In order to aid the user insliding the support 14' the support may include a finger tab 92 (shownin phantom in FIG. 11), a pull or other type of manually engageableextension, that extends slightly downwardly from the support, preferablyfrom a central area on the bottom of the support 14'. When the support14' is mounted on the housing 70, the tab 92 extends through a slotformed in the bottom wall of the housing 70 so that a user can engagethe tab 92 to slide the tab along the slot to thereby slide the support14' along a linear path relative to the housing 70. With the support 14'housing 70 and frame 72, each of the lenses 20, 22 is moveably mountedin the support 14' as discussed above with respect to the support 14,the support 14' is moveable along a linear path with respect to thehousing 70 and thus with respect to the user's eyes; and the housing 70,support 14' and lens-display pairs are rotatable about an axis extendingthrough the protrusions 74 and 76. The head mounted display system 10 ofthe present invention is thus adjustable so as to accommodate varioususers and to accommodate various positions on a user's head.

It is noted that the optical system described above may be made so as tosee through by merely rotating each aspheric lens and display pairninety degrees relative to the user's eye and adding in each opticalpath a partial reflector, such as a semi-reflective mirror, at a fortyfive degree angle with respect to the user's eye and the face of therespective lens. Such a system is illustrated in FIG. 12 for theaspheric lens 20-display 24 pair and a reflector 94. Other variationsmay also be made in the system without departing from the scope of theinvention. For example, although a binocular head mounted display systemis shown and described herein in detail, a number of the features of thepresent invention are not limited to a binocular system, but areapplicable to a head mounted display unit that is monocular as well.Further, although the binocular head mounted display system shownutilizes two separate displays, one in association with each of theaspheric lenses, the aspheric lenses taught above may be used in anysystem for mapping a flat displayed image onto the complex curvature ofthe user's retina so as to provide a virtual image with minimaldistortions therein. Many other modifications and variations of thepresent invention may be made. Thus, it is to be understood, that,within the scope of the appended claims, the invention may be practicedotherwise than described herein above.

What is claimed and desired to be secured by Letters Patent is:
 1. Abinocular head mounted display system comprising:a support to mount thedisplay system on a user's head; a right-eye aspheric lens mounted onsaid support so as to be positioned in front of a user's right eye andat a convergence angle with respect to said user's right eye to directsaid eye inward; a right-eye display for depicting video informationmounted on said support at a distance from said right-eye lens with theface of said display generally parallel to said right-eye lens such thatthe user views an image of the video from the right-eye display throughthe right-eye lens with the user's right eye directed inward by saidconvergence angle, said right-eye aspheric lens providing an enlargedimage of the video information from said right-eye display with minimaldistortions therein; a left-eye aspheric lens mounted on said support soas to be positioned in front of a user's left eye and at a convergenceangle with respect to said user's left eye to direct said eye inward;and a left-eye display for depicting video information mounted on saidsupport at a distance from said left-eye lens with the face of saiddisplay generally parallel to said left-eye lens such that the userviews an image of the video from the left-eye display through theleft-eye lens with the user's left eye directed inward by saidconvergence angle, said left-eye aspheric lens providing an enlargedimage of the video from said left-eye display with minimal distortionstherein.
 2. A binocular head mounted display system as recited in claim1 further including means for independently varying the distance betweensaid right-eye lens and display and the distance between said left-eyelens and display while maintaining the face of each display generallyparallel to its respective lens.
 3. A binocular head mounted displaysystem as recited in claim 2 wherein each of said displays is fixedlymounted on said support and each of said lenses is movably mounted onsaid support to vary the distance between the lens and the respectivedisplay.
 4. A binocular head mounted display system as recited in claim1 further including means for moving said support with respect to theuser's face to allow a user to vary the distance between the user's eyesand respective lenses.
 5. A binocular head mounted display system asrecited in claim 1 wherein said displays are stereoscopic displays.
 6. Abinocular head mounted display system comprising:a support to mount thedisplay system on a user's head; a right-eye lens mounted on saidsupport so as to be positioned in front of a user's right eye and at aconvergence angle with respect to said user's right eye to direct saideye inward; a right-eye display for depicting video information mountedon said support at a distance from said right-eye lens with the face ofsaid display generally parallel to said right-eye lens such that theuser views an image of said video from the right-eye display through theright-eye lens with the user's right eye directed inward by saidconvergence angle; a left-eye lens mounted on said support so as to bepositioned in front of a user's left eye and at a convergence angle withrespect to said user's left eye to direct said eye inward; a left-eyedisplay for depicting video information mounted on said support at adistance from said left-eye lens with the face of said display generallyparallel to said left-eye lens such that the user views an image of thevideo from the left-eye display through the left-eye lens with theuser's left eye directed inward by said convergence angle; and amounting fixture for mounting said right and left eye lenses and saidright and left eye displays on said support such that said lenses anddisplays are movable together along a linear path generally parallel toan axis extending through one of said lenses and the user's respectiveeye to vary the position of the lenses and displays relative to theuser's eyes without altering the position of the right-eye lens relativeto the right-eye display and the position of the left-eye lens relativeto the left-eye display.
 7. A binocular head mounted display system asrecited in claim 6 wherein the distance between said right-eye lens anddisplay and the distance between said left-eye lens and display areindependently variable while maintaining the face of each displaygenerally parallel to its respective lens.
 8. A binocular head mounteddisplay system as recited in claim 7 wherein each of said displays isfixedly mounted on said support and each of said lenses is movablymounted on said support to vary the distance between the lens and therespective display.
 9. A binocular head mounted display system asrecited in claim 6 wherein said lens is biconvex.
 10. A binocular headmounted display system as recited in claim 6 wherein said lens is anachromat.
 11. A head mounted display system comprising:a support tomount the display system on a user's head; an image source mounted onsaid support for providing video information in a flat image plane; andan aspheric lens mounted on said support relative to said image sourcefor providing an enlarged image of said video projected at a distanceform the user, said aspheric lens having a surface shaped with aplurality of concentric zones including an inner-zone for substantiallycontrolling the distance from the user at which a virtual image appearsand a zone located outside of said inner-zone for minimizing distortionsacross said virtual image so as to map the flat video image onto thecomplex curvature of the user's retina.
 12. A head mounted displaysystem as recited in claim 11 wherein said aspheric lens is biasphericincluding an aspheric entrance surface and an aspheric exit surface. 13.A head mounted display system as recited in claim 11 wherein saidaspheric lens is formed of at least two materials having differentindices of refraction so as to form an achromat to compensate forchromatic aberrations.
 14. A head mounted display system as recited inclaim 11 wherein said image source is a display having a face on whichsaid video is depicted, said aspheric lens and display being mounted onsaid support generally parallel to each other and at a convergence anglewith respect to a user's eye so as to direct the user's eye inward toview the virtual image.
 15. A head mounted display system comprising:asupport to mount the display system on a user's head; a right-eye imagesource mounted on said support for providing video information; aright-eye aspheric lens mounted on said support relative to saidright-eye image source for providing an enlarged image of the video fromsaid right-eye source projected at a distance form the user, saidright-eye aspheric lens having a surface shaped with a plurality ofconcentric zones including an inner-zone for substantially controllingthe distance from the user at which a virtual image appears and a zonelocated outside of said inner-zone form minimizing distortions acrosssaid virtual image; a left-eye image source mounted on said support forproviding video information; and a left-eye aspheric lens mounted onsaid support relative to said left-eye image source for providing anenlarged image of said video from said left-eye source projected at adistance from the user, said left-eye aspheric lens having a surfaceshaped with a plurality of concentric zones including an inner-zone forsubstantially controlling the distance from the user at which saidvirtual image appears and a zone located outside of said inner-zone forminimizing distortions across said virtual image.
 16. A head mounteddisplay system as recited in claim 15 wherein each of said asphericlenses is biaspheric including an aspheric entrance surface and anaspheric exit surface.
 17. A head mounted display system as recited inclaim 15 wherein each of said aspheric lenses is formed as an achromatto compensate for chromatic aberrations.
 18. A head mounted displaysystem as recited in claim 15 wherein each of said image sources is adisplay having a face on which said video is depicted, each asphericlens and display pair being mounted on said support such that the lensof the pair is generally parallel to the display of the pair and at aconvergence angle with respect to a user's eye so as to direct theuser's eyes inward to view a virtual image.
 19. A head mounted displaysystem comprising:a support to mount the display system on a user'shead; an image source mounted on said support for providing videoinformation; and an aspheric lens mounted on said support relative tosaid image source for providing an enlarged image of said videoprojected at a distance from the user, said aspheric lens having asurface shaped with a plurality of concentric zones including aninner-zone for substantially controlling the distance from the user atwhich a virtual image appears, a mid-zone for minimizing variations inmagnification across said virtual image and an outer-zone for minimizingdistortions in the edges of said virtual image.
 20. A head mounteddisplay system as recited in claim 19 wherein said aspheric lens isbiaspheric including an aspheric entrance surface and an aspheric exitsurface.
 21. A head mounted display system as recited in claim 19wherein said aspheric lens is an achromat to compensate for chromaticaberrations.
 22. A head mounted display system as recited in claim 19wherein said image source is a display having a face on which said videois depicted, said aspheric lens and display being mounted on saidsupport generally parallel to each other and at a convergence angle withrespect to a user's eye so as to direct the user's eye inward to viewthe image.
 23. A head mounted display system as recited in claim 19wherein said inner-zone is substantially spherical.
 24. A head mounteddisplay system as recited in claim 23 wherein said mid-zone is flatterthan said inner-zone.
 25. A head mounted display system as recited inclaim 24 wherein said outer-zone is more curved than said mid-zone. 26.A head mounted display system as recited in claim 19 wherein said lensis biaspheric with more power in an entrance surface of said lensadjacent to said display than the power in an exit surface of the lensadjacent to the user's eyes.
 27. A head mounted display system asrecited in claim 19 wherein the support for said lens and image sourcehas a thickness from a front surface to a back surface that is less thanapproximately 2 inches.
 28. A head mounted display system comprising:asupport to mount the display system on a user's head; an image sourcemounted on said support for providing video information; and an asphericlens mounted on said support relative to said image source such thatsaid video information is directed to a user's eye through said asphericlens, said aspheric lens providing an enlarged image of the videoinformation, said aspheric lens having a surface shaped with a pluralityof concentric zones including an inner zone for substantiallycontrolling the distance from the user at which said image appears, amid-zone for minimizing variations in magnification across a virtualimage and an outer zone for minimizing distortion in the edges of saidvirtual image.
 29. A head mounted display system as recited in claim 28including a reflector mounted on said support relative to said asphericlens to allow said user to view said image through said reflector.
 30. Ahead mounted display system as recited in claim 29 wherein saidreflector is partially reflective.
 31. A head mounted display system asrecited in claim 29 wherein said reflector is fully reflective.
 32. Ahead mounted display system as recited in claim 28 wherein said asphericlens is positioned between said image source and a user's eye to allowthe user to view through said aspheric lens said enlarged image.
 33. Ahead mounted display system as recited in claim 28 herein said headmounted display system is a binocular system and further includes asecond aspheric lens mounted on said support relative to said imagesource such that said video information is directed to the user's othereye through said second aspheric lens.
 34. A head mounted display systemas recited in claim 33 wherein said image source includes a firstdisplay and a second display.
 35. A head mounted display system asrecited in claim 28 wherein the distance between said aspheric lens andsaid image source is variable.
 36. A head mounted display system asrecited in claim 28 wherein the distance between said aspheric lens anda user's eye is variable when said support is mounted on the user'shead.
 37. A head mounted display system as recited in claim 28 whereinsaid aspheric lens and image source are mounted on said support so as tobe rotatable together to vary the position of the aspheric lens and theimage source relative to the user's eye without altering the position ofthe aspheric lens relative to said image source.
 38. A head mounteddisplay system comprising:a support to mount the display system on auser's head; an image source mounted on said support for providing videoinformation; an aspheric lens mounted on said support relative to saidimage source such that said video information is directed to a user'seye through said aspheric lens, said aspheric lens providing an enlargedimage of the video information; means for mounting said aspheric lens onsaid support such that said aspheric lens and image source are movabletogether along a linear path generally parallel to an axis extendingthrough said lens and the user's eye and are rotatable together about anaxis of rotation to vary the position of the aspheric lens and the imagesource relative to the user's eye without altering the position of theaspheric lens relative to the image source; and means for varying thedistance between said aspheric lens and said image source.